Maternal immunity to red cell antigens and fetal transfusion

This article has presented an overview of developments in the treatment of HDN. The number of cases requiring treatment that have occurred in the last decade has dropped because of the development and implementation of Rh immunoprophylaxis, although this treatment still appears to be underutilized in the United States. Failure to recognize the need for immunoprophylaxis in certain situations (including unrecognized abortion) has led to a small residual population of alloimmunized mothers who will require comprehensive treatment during subsequent pregnancies. Alloimmunization to other red cell antigens remains a small but significant problem in other women. Although great advances have been made in the monitoring of these pregnancies, amniotic fluid analysis remains a mainstay for the third-trimester evaluation of alloimmunized pregnancies. Noninvasive methods such as ultrasound evaluation and the monocyte assays may supplement, but cannot entirely replace, the need for direct assessment. The most striking advancement in the evaluation and treatment of these infants has been the ability to access the fetal circulation directly through intravenous umbilical cord sampling. This method allows for an immediate assessment of fetal anemia as well as a route for direct fetal transfusion. The method has also permitted a more complete assessment of fetal physiology. However, the method may be overutilized at the present time and has some degree of risk to the fetus, even in experienced hands. Additional methods of treatment for the alloimmunized pregnancy include plasma exchange, intravenous immunoglobulin infusion, and promethazine hydrochloride. The popularity of plasma exchange has probably decreased with the advent of more direct fetal sampling and treatment techniques, but it may be useful in the treatment of first-trimester pregnancy losses. Intravenous immunoglobulin and promethazine hydrochloride appear to be promising alternatives that require more investigation. It is apparent that efforts need to be channeled towards prevention of HDN in a health system that is highly aware of increasing costs and the benefits of preventive medicine.